As a free user, I can upload 10 megs a month, and am limited to three sets. 10 megs seems to be plenty so far, but three sets is bad. Here are my three. One might argue that sets defeats the purpose of the tagging, as tagging makes it easy for someone to search, and eliminates the needs for sets. I would argue that sets are what makes it easiest to share new photos as "albums." I also hear that Flicrk is cool since it has a strong API, which makes it easy for programmers to write tools that integrate with it.
Anyway, the three set limitation is bugging me, so I've been exploring options. Gallery looks pretty slick, and I think I could throw it on my home server, but I don't think it has the tags, nor does it have the community that Flickr does - on the other hand, I'd have unlimited albums, nested albums, and movie support. I'll mess with it when I get a chance - I've noticed I spend a lot less time messing around with computers these days, which has pros and cons . . .